Paleomagnetism of the Proterozoic Wathaman batholith and the suturing of the Trans-Hudson orogen in Saskatchewan

1991 ◽  
Vol 28 (12) ◽  
pp. 1931-1938 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Oceanic Crust ◽  
Remanent Magnetization ◽  
Shear Zones ◽  
Pole Position ◽  
Superior Province ◽  
Isothermal Remanent Magnetization ◽  
Early Proterozoic ◽  
Magmatic Arc ◽  
Flin Flon ◽  
Lynn Lake

The Wathaman (Wathaman–Chipewyan) batholith is an 1854 ± 11 Ma, northeast-trending, homogenous, felsic pluton that is over 900 km long. It is thought to be a magmatic arc, with the Archean Hearne craton on its northwestern side as the hinterland and the remains of the Early Proterozoic Manikewan oceanic crust of the Trans-Hudson orogen on its southeastern side. Alternating-field and thermal step demagnetization methods isolate an A remanence component with a mean direction of D = 134.6°, I = 54.1° (α95 = 3.5°, k = 94, N = 19). Isothermal remanent magnetization tests confirm that this A magnetization component is preserved in pseudosingle to multidomain magnetite and in hematite. Contact tests with intruded older rocks of the Peter Lake domain, with younger crosscutting mafic dikes and with younger crosscutting shear zones, indicate that A is a primary remanence. Its pole position of 67°W, 9°N (dp = 3°, dm = 5°) confirms that it was formed along the margin of the Slave–Rae–Hearne craton, supporting tectonic models that it records a suture zone. It also indicates that the LaRonge – Lynn Lake domain, Flin Flon domain, and Superior Province were translated relatively northwestward into the suture by at least 11 ± 11°, 27 ± 12°, and 49° ± 16°, respectively, as the Manikewan Ocean closed.

Rb–Sr study of metavolcanic rocks from the La Ronge and Flin Flon domains, northern Saskatchewan

1985 ◽  
Vol 22 (3) ◽  
pp. 452-463 ◽  
Author(s):  
B. R. Watters ◽  
R. L. Armstrong
Keyword(s):  
Source Region ◽  
Volcanic Rocks ◽  
Volcanic Arcs ◽  
Magmatic Arc ◽  
Linear Evolution ◽  
Metavolcanic Rocks ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Flin Flon ◽  
Lynn Lake

Two whole-rock suites of metavolcanic rocks from separate volcanic belts of the Churchill Province in northern Saskatchewan have been dated by Rb–Sr. Samples from the Amisk Group of the Flin Flon – Snow Lake domain provide an isochron date of 1784 ± 44 Ma; suites from the Waddy Lake and Devil Lake areas of the La Ronge (–Lynn Lake) domain yield isochron dates of 1814 ± 26 and 1854 ± 100 Ma, respectively. All are regarded as minima for, but close approximations to, emplacement ages. The maximum crustal age of any suite cannot greatly exceed 1850 Ma.Previous Rb–Sr and U–Pb isotopic dates together with these new determinations confirm the contemporaneous existence of two volcanic arcs, active during the late Aphebian (1875–1784 Ma) in the Churchill Province.Low initial 87Sr/86Sr ratios (0.7017–0.7022) are consistent with a petrochemically inferred subduction-related origin for the volcanic rocks with no closed-system reworking of Archean crust, and a linear evolution of 87Sr/86Sr ratio in the magmatic-arc mantle source region from 4.55 Ga to the present.

Age of the Firesand River carbonatite complex from paleomagnetism

1989 ◽  
Vol 26 (11) ◽  
pp. 2401-2405 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Blocking Temperature ◽  
Isothermal Remanent Magnetization ◽  
Carbonatite Complex ◽  
Polar Wander ◽  
Partial Contact ◽  
Apparent Polar Wander Path ◽  
Temperature Spectra ◽  
Middle Proterozoic

The 2.3 km diameter Firesand River complex intrudes Archean volcanics and granites of the Wawa Subprovince in the Superior Province about 8 km east of Wawa, Ontario. It has given differing Middle Proterozoic K–Ar biotite ages of 1018 ± 50 and 1097 Ma. Alternating-field and thermal step demagnetization of specimens from three calcific carbonatite sites, five ferruginous dolomitic carbonatite sites, and one lamprophyre dike site isolated a stable mean direction of 290°, 33 °(α95 = 12°). Isothermal remanent magnetization tests indicate the remanence is held by single-to pseudosingle-domain magnetite and hematite in the carbonatite. The dike remanence is Keweenawan in age, thereby confirming its genetic relationship to the complex, and it gives a positive partial contact test with its host rock, indicating no postintrusive remagnetization. The blocking-temperature spectra indicate that postintrusive uplift has not exceeded about 4 km. The pole position for the complex is 183°E, 27°N (dp = 8°, dm = 13°). This pole lies directly on the well-dated Keweenawan apparent polar wander path, giving an age of 1090 ± 10 Ma, in agreement with the older K–Ar age. It also confirms geologic and aeromagnetic evidence that the complex has not been tectonically tilted since emplacement.

Paleomagnetism of the Keweenawan Chipman Lake and Seabrook Lake carbonatite complexes, Ontario

1992 ◽  
Vol 29 (6) ◽  
pp. 1215-1223 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Pole Position ◽  
Alteration Zone ◽  
Contact Aureole ◽  
Isothermal Remanent Magnetization ◽  
Abitibi Subprovince ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
Host Rocks

The Chipman Lake complex crops out as a series of carbonatite and related alkalic mafic dikes in the Wabigoon Subprovince of the Superior Province, whereas the Seabrook Lake complex crops out as an alkalic syenite – carbonatite stock in the Abitibi Subprovince. Paleomagnetic analysis was done on specimens from 23 and 19 sites located in and around the Chipman Lake and Seabrook Lake complexes, respectively, using detailed alternating-field and thermal step demagnetization and isothermal remanent magnetization tests. Contact tests with adjacent Archean host rocks show that both complexes retain a primary characteristic remanence (ChRM). The Chipman Lake's ChRM is retained in 11 dikes with normal polarity and one dike with reversed polarity and at one site with normal polarity and one site with reversed polarity from the fenite alteration zone. Its ChRM gives a pole position at 186°E, 38°N (dp = 7°, dm = 11°), which corresponds to a Keweenawan age of 1098 ± 10 Ma, suggesting that younger K–Ar amphibole ages do not date emplacement. The ChRM of the host rock, the Chipman Lake diorite stock, gives a pole at 49°E, 51°N (dp = 8°, dm = 13°), showing that it is not part of the Keweenawan complex but may be a 2.45 Ga Matachewan intrusive. The Seabrook Lake complex's ChRM is found at six normal polarity sites from within the complex and at four normal and three reversed polarity sites from within the fenitized Archean granite and Matachewan diabase of the contact aureole. It gives a pole position at 180°E, 46°N (dp = 11°, dm = 17°), which corresponds to a Keweenawan age of 1103 ± 10 Ma, agreeing with K/Ar biotite ages. The paleomagnetic data indicate that no significant motion on the Kapuskasing Structural Zone occurred after emplacement of the complexes excluding minor vertical uplift of less than about 4 km, and that there were multiple polarity transitions of a symmetric Earth's magnetic field during Keweenawan time.

Terrane accretion in the internal zone of the Ungava orogen, northern Quebec. Part 2: Structural and metamorphic history

1992 ◽  
Vol 29 (4) ◽  
pp. 765-782 ◽  
Author(s):  
S. B. Lucas ◽  
M. R. St-Onge
Keyword(s):  
Granulite Facies ◽  
Lower Plate ◽  
Superior Province ◽  
Thrust Belt ◽  
Granulite Facies Metamorphism ◽  
Early Proterozoic ◽  
Magmatic Arc ◽  
Facies Metamorphism ◽  
Transcurrent Deformation ◽  
External Part

The tectonic history of the early Proterozoic Ungava orogen is marked by structural–metamorphic episodes that both predate and postdate a collision between a magmatic arc terrane and the northern continental margin of the Superior Province. Distinct precollisional tectonic histories are documented for the rocks forming the lower plate of the Ungava orogen (the Archean Superior Province basement and an Early Proterozoic rift-to-drift margin sequence) and the orogenic upper plate (Early Proterozoic ophiolitic and magmatic arc units). The lower-plate units preserved in the external part of the orogen (Cape Smith Thrust Belt) record the development of a foreland thrust belt characterized by south-verging faults ramping up from a basal décollement located at the basement–cover contact. The plutonic core of the magmatic arc contains structures and metamorphic assemblages indicative of an episode of dextral transcurrent deformation contemporaneous with granulite-facies metamorphism and arc plutonism. The "tectonically suspect" ophiolitic and arc units were accreted to the thrust belt along south-verging faults, which reimbricated the foreland thrust belt and which resulted in at least 100 km of displacement of upper-plate units with respect to the autochthonous basement. Collisional thickening and consequent exhumation resulted in relatively high-pressure, greenschist- to amphibolite-facies metamorphism of lower-plate cover units, and in the retrogression of high-grade assemblages in the arc rocks. Postaccretion shortening resulted in folding of both the allochthonous rocks and the footwall basement.

Accretion history of the Trans-Hudson Orogen in Manitoba and Saskatchewan from paleomagnetism

2005 ◽  
Vol 42 (4) ◽  
pp. 723-740 ◽  
Author(s):  
David TA Symons ◽  
Michael J Harris
Keyword(s):  
Tectonic Evolution ◽  
Polar Wander ◽  
Magmatic Arc ◽  
Apparent Polar Wander Path ◽  
History Of ◽  
Andean Type ◽  
Flin Flon ◽  
Lynn Lake ◽  
Continental Magmatic Arc ◽  
Initial Framework

Lithoprobe's sponsorship has led to the acquisition of paleomagnetic data from ~20 units throughout the Paleoproterozoic Trans-Hudson Orogen (THO) of Saskatchewan and Manitoba, essentially the first such data for the region. Discussed summarily in this paper, they provide an initial framework for the THO's tectonic evolution. They show that the Archean Hearne and Superior cratons were at subtropical and subpolar paleolatitudes, respectively, at ~1875 Ma, with the Lynn Lake – LaRonge arc midway between them in the Manikewan Ocean. By ~1855 Ma, this ocean was still ~5500 ± 700 km wide, and its seafloor was subducting northwestward under the Hearne craton and pericratonic Peter Lake domain margin with the coeval development of an Andean-type continental magmatic arc, the Wathaman–Chipewyan batholith. Between ~1855 and ~1810 Ma, coalescing apparent polar wander path (APWP) segments record closing of the ocean at a rate of ~12 cm/a, trapping and accreting the several separate intervening terranes (Flin Flon, Hanson Lake, Lynn Lake – LaRonge, Rottenstone, and presumably also other THO terranes). From ~1815 to ~1775 Ma, the assembled terranes drifted as a coherent craton, yielding a stillstand and hairpin in the APWP.

Paleomagnetism of the Eocene Kamloops Group and the cratonization of Terrane I of the Canadian Cordillera

1989 ◽  
Vol 26 (4) ◽  
pp. 821-828 ◽  
Author(s):  
D. T. A. Symons ◽  
M. R. Wellings
Keyword(s):  
North American ◽  
Remanent Magnetization ◽  
Middle Eocene ◽  
Pole Position ◽  
Canadian Cordillera ◽  
Isothermal Remanent Magnetization ◽  
Clockwise Rotation ◽  
Saturation Isothermal Remanent Magnetization ◽  
The North ◽  
North American Craton

The lower Middle Eocene (49.4 ± 2.4 Ma) Kamloops Group is exposed in the middle of the Quesnellia subterrane of Terrane I. The group consists of the siliciclastic Tranquille Beds and the overlying Dewdrop Flats plateau basalts and andesites. Detailed alternating field (AF) and thermal step demagnetization was carried out on 282 specimens from 26 flow sites and one conglomerate site, and saturation isothermal remanent magnetization (SIRM) tests were performed to examine the remanence carriers. The petrology of the gently dipping flows, the presence of antiparallel normal and reverse remanence, the conglomerate test, and the fold test all indicate that a primary remanence has been isolated. It resides in both magnetite and hematite over a broad range of AF coercivities, blocking temperatures, and domain sizes. Its mean direction of 355.0°, 73.4 °(α95 = 6.9°) gives a pole position of 138.4°W, 81.4°N (dp = 11.0°, dm = 12.3°) that is statistically indistinguishable from the 50 Ma reference pole for the North American craton. This indicates that the cratonization of Terrane I was complete by the Middle Eocene after it had undergone ~1300 km of northward translation and ~45 °of clockwise rotation since the mid-Cretaceous.

Paleomagnetism of the Callander Complex and the Cambrian apparent polar wander path for North America

1991 ◽  
Vol 28 (3) ◽  
pp. 355-363 ◽  
Author(s):  
D. T. A. Symons ◽  
A. D. Chiasson
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Canadian Shield ◽  
Complete Spectrum ◽  
Isothermal Remanent Magnetization ◽  
Alkaline Complex ◽  
Grenville Province ◽  
Polar Wander ◽  
The Core ◽  
Apparent Polar Wander Path

The 7 km2 circular Callander alkaline complex was emplaced into anorthositic and granitic gneisses of the Grenville Province in the Canadian Shield about 575 ± 5 Ma ago at the start of the Cambrian. The complex has not been subsequently metamorphosed or tilted. Detailed alternating-field and thermal step demagnetization of 252 specimens from 29 sites led to the identification of a characteristic A magnetization component with a direction of D = 82.2°, I = 82.7° (α95 = 3.1°, k = 83, N = 26 sites) in 5 sites of mesocratic to leucocratic syenite from the core of the complex, in 5 sites of fenitized host rock from its aureole, and in 16 sites of lamprophyre from radiating dikes. Isothermal remanent-magnetization tests show that the A component is retained by both magnetite and hematite in a complete spectrum of domain sizes. A reversals test suggests and a contact test shows the A component to be primary. Its pole position at 46.3°S, 121.4°E(dp = 5.9°, dm = 6.1°) does not fall on published but poorly defined Cambrian apparent polar wander paths, leading to speculation on an alternative Cambrian path.

The Wathaman batholith: largest known Precambrian pluton

1984 ◽  
Vol 21 (10) ◽  
pp. 1082-1097 ◽  
Author(s):  
S. L. Fumerton ◽  
M. R. Stauffer ◽  
J. F. Lewry
Keyword(s):  
Shear Zones ◽  
Island Arc ◽  
Pacific Rim ◽  
Early Proterozoic ◽  
Northern Saskatchewan ◽  
Internal Deformation

The Early Proterozoic Wathaman batholith, in northern Saskatchewan and Manitoba, is a 900 km long, megacrystic granite–granodiorite intrusion that straddles the junction between ensialic miogeoclinal and probably ensimatic eugeoclinal–island-arc terranes of the "Trans-Hudson Orogen," of the western Churchill Province. Although the largest Precambrian batholith known, it is, apart from marginal complexities, remarkably homogeneous throughout and, unlike comparably sized and situated Phanerozoic batholiths, shows no evidence of multiple intrusion, nor does it have comagmatic early mafic phases. However, it may be considered as just one phase of a larger batholithic belt that also includes numerous smaller plutons. Taken as a whole the composite batholithic belt is similar in many aspects to Mesozoic Pacific rim batholithic belts, and like them probably was emplaced during plate collision.The batholith is affected by pervasive internal deformation, is bounded on the northwest by major blastomylonite zones, and is transected internally by splaying shear zones. It is a mid- to late-synkinematic Hudsonian intrusion, emplaced within a markedly compressional, crustal regime. On the basis of petrological, geochemical, and isotopic criteria the batholith is an "I-type" intrusion, but the origin of the magma and the emplacement mechanisms are still unresolved problems.

A structural reappraisal of the Beardmore–Geraldton Belt at the southern boundary of the Wabigoon subprovince, Ontario, and implications for gold mineralization

2004 ◽  
Vol 41 (2) ◽  
pp. 217-235 ◽  
Author(s):  
Bruno Lafrance ◽  
Jerry C DeWolfe ◽  
Greg M Stott
Keyword(s):  
Gold Mineralization ◽  
Shear Zones ◽  
Axial Plane ◽  
Superior Province ◽  
Southern Boundary ◽  
Gold Mines ◽  
Southern Margin ◽  
Ore Zones

The Beardmore–Geraldton Belt occurs along the southern margin of the Archean Wabigoon subprovince, Superior Province, Ontario. The belt consists of shear-bounded interleaved metasedimentary and metavolcanic units. The units were imbricated from 2696 to 2691 Ma during D1 thrusting and accretion of the Wabigoon, Quetico, and Wawa subprovinces. Post-accretion D2 deformation produced regional F2 folds that transposed lithological units parallel to the axial plane S2 cleavage of the folds. During D3 deformation, the folds were overprinted by a regional S3 cleavage oriented anticlockwise of F2 axial planes, and lithological contacts and S2 cleavage were reactivated as planes of shear within dextral regional shear zones that generally conform to the trend of the belt. D3 is a regional dextral transpression event that also affected the Quetico and Wawa subprovinces, south of the Beardmore–Geraldton Belt. Gold mineralization at the Leitch and MacLeod-Cockshutt mines, the two richest past-producing gold mines in the Beardmore–Geraldton Belt, is associated with D3 shear zones and folds, overprinting regional F2 folds. The plunge of the ore zones is parallel to F3 fold axes and to the intersection of D3 shear zones with F2 and F3 folds.

Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Stark Formation

1976 ◽  
Vol 13 (4) ◽  
pp. 563-578 ◽  
Author(s):  
D. K. Bingham ◽  
M. E. Evans
Keyword(s):  
Northwest Territories ◽  
North American ◽  
Geomagnetic Field ◽  
Pole Position ◽  
The West ◽  
Stratigraphic Sequence ◽  
Polar Wander ◽  
Early Proterozoic ◽  
The North ◽  
Polarity Reversals

Paleomagnetic results from 55 sampling sites throughout the Stark Formation are reported. The known stratigraphic sequence of these sites enables the behaviour of the geomagnetic field in these remote times (1750 m.y.) to be elucidated. Two polarity reversals are identified and these represent potentially useful correlative features in strata devoid of index fossils. One of these is investigated in detail and indicates that behaviour of the geomagnetic field during polarity reversals was essentially the same in the early Proterozoic as it has been over the last few million years. The pole position (145°W, 15°S, dp = 3.5, dm = 6.9) lies far to the west of that anticipated from earlier results, implying further complexity of the North American polar wander curve. Possible alternatives to this added complexity are discussed.

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